Storm sewer systems typically include catch basins to collect surface runoff water. Catch basins may be shallow below-ground wells or pits with inlets at surface level, for example, in streets or in sidewalks, and with outlets draining into larger storm sewers, streams, or other bodies of water.
Catch basins may collect surface runoff water, such as precipitation, melt water and waste water. Inflowing water may carry entrained sediment which may include dirt, sand, litter, or other waste. Catch basins are often designed with a sump in which water pools to promote settling of sediment so that sediment may be removed from the basin and disposed of, rather than being carried downstream by water flowing out of the catch basin. Water may pool in the sump and remain substantially undisturbed for extended periods (e.g. hours or days) when surface runoff is slow or absent.
Events such as storms, spring melt or the like may periodically cause water to flow into catch basins at relatively high rates. High flow rate or fast-flowing water may agitate sump pools in conventional catch basins, causing accumulated sediment to mix with and be carried away by water flowing out of the sump. Such conditions may limit the effectiveness of catch basins for capturing and removing sediment and may result in sediment being deposited, for example, on streets, in streams, or the like.